The embodiments relate to an assembly, in particular an aircraft assembly, comprising a plurality of individual components composed of a fibre-reinforced composite material. Furthermore, the embodiment relates to a method for producing such an assembly. In aircraft construction, efforts are being made to use increasingly components which are composed wholly or partly of fibre-reinforced composite materials, for example glass fibre- or carbon fibre-reinforced plastics. For example, DE 10 2007 062 111 A1 describes a transverse support structure which is composed of carbon fibre-reinforced plastic and serves to support the individual panels of an aircraft floor system for separating a passenger cabin from a cargo compartment arranged below the passenger cabin. Furthermore, it is known, for example from DE 10 2004 001 078 B4 or CN 100418850, to produce aircraft fuselage segments, which comprise an aircraft outer skin section and reinforcing elements (e.g. frames, stringers), from fibre-reinforced composite materials.
In the production of aircraft components from fibre-reinforced composite materials, a multilayer laminate is firstly built up from fibre prepregs. The fibre prepregs may comprise a woven fabric or laid fabric of reinforcing fibres provided with a surface layer made of a curable plastics material. The laminate may be built up manually or in an automated manner, supporting and holder structures frequently being required in particular in the production of components of complex shapes, in order to bring the components into the desired shape. The plastics material deposited on the surfaces of the fibres is finally cured in an autoclave cycle under pressure and/or elevated temperature, so that a composite material with a matrix made of cured plastic and reinforcing fibres embedded in the matrix is obtained.
In the production of aircraft fuselage segments described in DE 10 2004 001 078 B4 or CN 100418850, a reinforcing-element semifinished product composed of a fibre prepreg may be brought into the desired shape and subsequently, as described above, subjected to an autoclave cycle in order to cure the plastics material contained in the reinforcing-element semifinished product. The reinforcing element may then be placed onto an aircraft outer skin section semifinished product likewise composed of a fibre prepreg and, by curing the plastics material contained in the aircraft outer skin section semifinished product, in a further autoclave cycle, connected to the aircraft outer skin section semifinished product or the aircraft outer skin section resulting from the semifinished product. Finally, in a separate process step, exposed edges of the reinforcing element which have been produced for example by machining during the shaping, such as e.g. a milling or grinding process, must be sealed. For this purpose, a sealing resin in liquid form is applied to the edges and subsequently cured. In the cured state, the sealing resin protects the assembly from environmental influences, such as e.g. the penetration of moisture and other substances and moreover affords a certain, albeit limited, protection from mechanical impairments.
The embodiments described herein is directed to the object of providing an assembly, in particular an aircraft assembly, comprising a plurality of individual components composed of a fibre-reinforced composite material, which assembly can be produced simply and efficiently and moreover is distinguished by good stability in the region of its edges to be sealed. Furthermore, the embodiment is directed to the object of specifying a method for producing such an assembly.
This object is achieved by an assembly made of a fibre-reinforced composite material as disclosed herein.
An assembly comprises a plurality of individual components composed of a fibre-reinforced composite material. The assembly is in particular an aircraft assembly. For example, the assembly may be provided to form a fuselage segment of an aircraft and comprise an areal, correspondingly curved aircraft outer skin section and at least one reinforcing element, which may be configured for example in the form of a stringer or a frame. The reinforcing fibres contained in the fibre-reinforced composite material used to produce the individual components may, for example, be glass fibres, carbon fibres or other suitable reinforcing fibres. The fibres may be present in the form of continuous fibres, fibre bundles, fibre-laid fabrics or fibre-woven fabrics. In individual-component semifinished products used for producing the individual components, the fibres may be impregnated with a resin or another plastics material which can be cured by input of energy, resulting in a dimensionally stable composite material with a matrix made of the cured plastics material and reinforcing fibres embedded in the matrix.
In the production of the assembly, individual components already containing cured plastics material may be connected to one another. Preferably, however, in the production of the assembly at least one individual-component semifinished product is processed, which contains uncured plastics material and may be configured, for example, in the form of a fibre prepreg. For example, a first individual-component semifinished product may be pretreated in an autoclave, so that a first individual component configured e.g. in the form of a reinforcing element results. This first individual component can then be placed onto a second individual-component semifinished product configured e.g. in the form of an aircraft outer skin section semifinished product and, by curing the uncured plastics material contained in the second individual-component semifinished product, in a further autoclave cycle, connected to the second individual-component semifinished product or the second individual component resulting from the second individual-component semifinished product. Thereby, a reactive connection between a surface of the first and a surface of the second individual component can be produced.
At least one individual component of the assembly comprises an edge section which has been produced, for example, by machining the individual component, such as e.g. by milling. This edge section requires sealing in order to protect the assembly from environmental influences, such as e.g. the penetration of moisture. For example, a first individual component configured in the form of a reinforcing element may comprise at least one such edge section. In the assembly, an edge section of at least one individual component of the assembly is sealed by means of a sealing tape which contains reinforcing fibres and a curable plastics material.
In the production of the assembly, it is therefore no longer necessary to apply a liquid sealing resin to an exposed edge section of an individual component of the assembly which is to be sealed. Rather, the sealing tape in the form of a sealing-tape semifinished product containing the curable plastics material in the uncured state can be applied to the edge section in a comparatively simple manner, whereby the process for producing the assembly can be designed more efficiently. The curable plastics material contained in the sealing-tape semifinished product can then be cured by supplying energy, e.g. in an autoclave. This results in a uniform distribution of the curable plastics material contained in the sealing tape over the edge section to be sealed, whereby the quality of the edge sealing can be improved.
In principle, it is conceivable to apply the sealing-tape semifinished product to an edge section of an individual component of the assembly to be sealed, only when the assembly is otherwise finished, i.e. the assembly no longer comprises any individual-component semifinished products. The curable plastics material contained in the sealing-tape semifinished product then has to be cured in a separate process step. Preferably, however, the sealing-tape semifinished product is applied to an edge section of an individual component of the assembly to be sealed, already at a time at which the assembly still comprises at least one individual-component semifinished product and therefore still has to undergo a heat- and/or pressure-treatment step anyway, in order to cure the plastics material contained in the individual-component semifinished product. The curable plastics material contained in the sealing-tape semifinished product can then be cured simultaneously with the curable plastics material contained in the individual-component semifinished product, so that a separate process for curing the plastics material contained in the sealing-tape semifinished product can be dispensed with.
A further advantage of the assembly arises from the fact that the sealing tape contains, besides curable plastics material, reinforcing fibres and thereby protects the edge section sealed by means of the sealing tape better from mechanical loads than pure sealing resin. In particular, the use of the sealing tape containing reinforcing fibres increases the damage tolerance of the sealed edge section to collision, impact and shock loads.
The sealing tape preferably contains a curable resin, in particular an epoxy resin. If the curable plastics material contained in a sealing-tape semifinished product is to be cured simultaneously with a curable plastics material contained in an individual-component semifinished product of the assembly, the sealing-tape semifinished product preferably contains the same curable plastics material as the individual-component semifinished product. This enables optimal control of the curing process for curing the curable plastics material contained in the sealing-tape semifinished product and the individual-component semifinished product.
In a preferred embodiment of the assembly, the sealing tape contains less than 35 vol %, in particular 10 to 30 vol % and particularly preferably 15 to 20 vol % of reinforcing fibres. This ensures that the sealing tape contains a sufficient amount, i.e. a sufficient volume fraction, of curable plastics material. Proper sealing of the edge section, to which the sealing tape is applied, is thereby guaranteed.
At least a proportion of the reinforcing fibres contained in the sealing tape are preferably carbon fibres, in particular short carbon fibres. Additionally or alternatively thereto, the sealing tape may, however, also contain glass fibres or other reinforcing fibres which increase the mechanical strength of the sealing tape. Preferably, the proportion of carbon fibres in the total amount of the reinforcing fibres contained in the sealing tape is 85 to 95 vol %. The carbon fibres may be recycled fibres or new fibres or a mixture of recycled fibres and new fibres.
Furthermore, at least a proportion of the reinforcing fibres contained in the sealing tape can be composed of a thermoplastic plastics material. In particular, the sealing tape can contain polyamide fibres. Preferably, the proportion of the reinforcing fibres of a thermoplastic plastics material contained in the sealing tape is 5 to 15 vol % of the total fibre content. Fibres composed of a thermoplastic plastics material, in particular polyamide, increase the fracture toughness of the sealing tape and thus contribute to further improvement of the damage tolerance of the sealing tape, in particular in the case of collision, impact and shock loads.
In a preferred embodiment of the assembly, the sealing tape extends over the edge section to be sealed and over at least one surface section, adjacent to the edge section to be sealed, of at least one of the two individual components. A secure fastening of the sealing tape in the region of the edge section to be sealed is thereby ensured. Furthermore, “sharp” edges present in the region of the edge section are smoothed or rounded by the sealing tape. It is thereby possible to minimise the risk of a vacuum film, which is wound around the assembly, for example during an autoclave process for curing a curable plastics material contained in an individual-component semifinished product and/or a sealing-tape semifinished product, being damaged by a “sharp” edge of an edge section to be sealed. Finally, by using a sealing tape which extends over the edge section to be sealed and over at least one surface section, adjacent to the edge section to be sealed, of at least one of the two individual components, the peeling stress resistance of the connection between two individual components of the assembly in the region of the edge section to be sealed is increased.
In one embodiment of the assembly, the sealing tape may extend over an edge section, to be sealed, of a first individual component, a surface section, adjacent to the edge section to be sealed, of the first individual component and a surface section, adjacent to the edge section to be sealed, of a second individual component. In such a configuration of the assembly, the sealing tape or the sealing-tape semifinished product is preferably positioned over the edge section to be sealed and the corresponding adjacent surface sections of the individual components or individual-component semifinished products, only after the connection of the individual components or individual-component semifinished products to one another.
Alternatively or additionally thereto, the assembly may comprise a sealing tape which extends over an edge section, to be sealed, of a first individual component and two surface sections, adjacent to the edge section to be sealed, of the first individual component. For example, the sealing tape may extend over two mutually opposite surface sections of the first individual component which are adjacent to the edge section to be sealed. Such a placement of the sealing tape is suitable, for example, in the region of edge sections of an individual component of the assembly which are situated at a relatively large distance from other individual components of the assembly.
In a particular embodiment of the assembly, a region of the sealing tape extending over a first surface section of the first individual component is arranged between the first surface section of the first individual component and a surface section of the second individual component lying opposite the first surface section. A sealing-tape semifinished product can then be applied in a simple manner to the edge section and the first surface section, adjacent to the edge section, of the first individual component or a first individual-component semifinished product, before the first individual component or the first individual-component semifinished product is connected to the second individual component or a second individual-component semifinished product. As a result, the production of the assembly can be further simplified. In such a case, however, the sealing tape should be thin enough that the dimensions of the assembly are not appreciably affected by the arrangement of the sealing tape between a first surface section of the first individual component and a surface section of the second individual component lying opposite the first surface section. This can be ensured, for example, by the use of a sealing tape, the basis weight of which is 4 to 10 g/m2 and the thickness of which corresponds merely to approximately 1/10 of the thickness of a reinforcing fibre layer in one of the individual components of the assembly.
In a method for producing an assembly, in particular an aircraft assembly, which comprises a plurality of individual components composed of a fibre-reinforced composite material, an edge section of at least one of the two individual components is sealed by means of a sealing tape which contains reinforcing fibres and a curable plastics material.
In the method for producing an assembly, a sealing-tape semifinished product, which contains the curable plastics material in the uncured state, can be applied to the edge section. The curable plastics material contained in the sealing-tape semifinished product can then be cured simultaneously with a curable plastics material which is contained in an individual-component semifinished product and in particular is cured in a step for connecting the individual-component semifinished product to an individual component or a further individual-component semifinished product of the assembly so as to produce a reactive connection between a surface of the first and a surface of the second individual component.
Preferably, the sealing tape contains less than 35 vol %, in particular 10 to 30 vol % and particularly preferably 15 to 20 vol % of reinforcing fibres. Additionally or alternatively thereto, 85 to 95 vol % of the reinforcing fibres contained in the sealing tape may be carbon fibres, in particular short carbon fibres. Additionally or alternatively thereto, 5 to 15 vol % of the reinforcing fibres contained in the sealing tape may be fibres composed of a thermoplastic plastics material, in particular polyamide.
The sealing tape may be applied in such a way that it extends in the finished assembly over the edge section to be sealed and over at least one surface section, adjacent to the edge section to be sealed, of at least one of the two individual components.
The sealing tape may be applied, in particular after the connection of a first individual component or a first individual-component semifinished product to a second individual component or a second individual-component semifinished product, in such a way that it extends in the finished assembly over an edge section, to be sealed, of the first individual component, a surface section, adjacent to the edge section to be sealed, of the first individual component and a surface section, adjacent to the edge section to be sealed, of the second individual component.
The sealing tape may also be applied in such a way that it extends in the finished assembly over an edge section, to be sealed, of a first individual component and two surface sections, adjacent to the edge section to be sealed, of the first individual component.
In particular, before the connection of the first individual component or the first individual-component semifinished product to the second individual component or the second individual-component semifinished product, the sealing tape may be applied in such a way, and the first individual component or the first individual-component semifinished product may be subsequently connected to the second individual component or the second individual-component semifinished product in such a way, that in the finished assembly a region of the sealing tape extending over a first surface section of the first individual component is arranged between the first surface section of the first individual component and a surface section of the second individual component lying opposite the first surface section.